A couple of years ago I bought a container of shellac flakes for mixing my own. When I got home I discovered that there weren’t very many loose flakes in the container; most of them were stuck together in a fairly solid clump. In retrospect I probably should have just taken it back to the shop for a refund (or even better, paid more attention in the first place), but I didn’t. I was able to chip off enough for what I needed at the time, but it took a bit of work with some suitable tool or other (coughhammerandscrewdrivercough). Much more effort than I felt was worth using for the rest of it, so ever since I’ve still had this container of…well, a lump of shellac.

Is it pretty much a goner, or is there some way (that may or may not involve a bigger hammer) to break it up into usable flakes, or at least chunks, again?

-- Anyone who wants an excuse can find one. Don't bother telling me yours; I have enough of my own to fight off.

That’s what I would do as well, try to chip it apart and dissolve it, then see if it dries. Chances are you’re good to go, but your instinct to return it was right on. Shellac seems to have went up quite a bit lately (guess the bugs aren’t giving their all) so saving it may be a worthwhile effort. If you get it broken up, store it in the fridge…..that’s goes for the solution as well. Keeps a little longer that way.